DESCRIPTION: (Adapted from the Applicant's Description) The current proposal is based on the premise that a full understanding of the genetic architecture for many birth defects will only be obtained if "higher-order" effects such as gene-environment (GxE) interactions, gene-gene (GxG) interactions and maternal genotypic effects are evaluated in concert with more traditional epidemiological and genetic risk factors. Moreover, recent advances in molecular and statistical genetics provide a foundation upon which to build studies that address the role of higher-order effects, when such effects are suggested by current understanding of a disease's etiology. The investigators propose to evaluate the role of GxE interactions, GxG interactions and maternal effects in the etiology of two groups of birth defects: neural tube defects and cranial abnormalities including craniosynostosis and nonsynostotic posterior plagiocephaly (CSINSPP). These conditions were selected from other potential candidates because current understanding of their etiologies support multiple hypotheses regarding higher-order effects. Hence, for these conditions in particular, it is now feasible to begin to construct a multi- dimensional blueprint of their genetic architecture. They will use state-of- the-art genotyping methods, including high-throughput array technologies, and employ state-of-the-art statistical approaches to evaluate the role of higher- order effects in the etiology of spina bifida and CS/NSPP.